CN113433423B - T-shaped line voltage cross correction fault location method - Google Patents

T-shaped line voltage cross correction fault location method Download PDF

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CN113433423B
CN113433423B CN202110753528.6A CN202110753528A CN113433423B CN 113433423 B CN113433423 B CN 113433423B CN 202110753528 A CN202110753528 A CN 202110753528A CN 113433423 B CN113433423 B CN 113433423B
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CN113433423A (en
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李振兴
黄悦华
李振华
翁汉琍
张健婷
包文亮
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China Three Gorges University CTGU
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/088—Aspects of digital computing
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    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
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Abstract

A T-shaped line cross correction fault location method utilizes electrical information of a T-shaped line in a normal operation state to dynamically calculate real-time parameters of a three-end line in real time, and corrects calculation errors of the real-time parameters of the line based on a genetic algorithm; after the line has a fault, respectively calculating the voltage of the T node based on a line distribution parameter line model under the correction parameter, and judging a fault branch circuit through voltage comparison; then equating the two non-fault branches as a T end, and forming a two-end power transmission line model with one end of the fault branch; and finally, forming two straight lines by using the measured voltages at the two sides and the calculated voltage at the opposite side, and obtaining an intersection point based on the straight line intersection to form a fault distance measuring method. The invention can dynamically adjust the line parameter error in real time, improve the fault location precision and has strong engineering practicability.

Description

T-shaped line voltage cross correction fault location method
Technical Field
The invention relates to a fault location method for a T-shaped power transmission line, in particular to a fault location method for cross correction of line voltage of a T-shaped line.
Background
With the development of power systems, T-shaped power transmission lines are often used for power transmission when limited by the power supply radius, corridors, and the like. When a line fails, precision fault location plays an important role in safety, stability and economic operation of a power system (forest flood, wang zeng, double-circuit fault location principle of adopting a homodromous positive sequence fundamental frequency component [ J ]. the Chinese Motor engineering report 2011,31(4): 93-98.). At present, the electric transmission line distance measurement usually adopts line power frequency quantity electric parameters, but in actual operation, the electric parameters are easily influenced by environments such as weather, temperature, humidity, earth resistivity and the like to change dynamically. Therefore, line fault location accuracy based on fixed electrical parameters is influenced by different degrees, T-shaped power transmission line nodes are complex in structure, location influence is larger, and improvement of fault location accuracy is always a research hotspot. The current T-shaped transmission line fault distance measurement algorithm is basically carried out in two steps. Firstly, judging a fault branch, and secondly, equating a three-terminal line to a two-terminal line according to a judgment result to carry out distance measurement. However, when a fault occurs near the T node, especially via a high-resistance short circuit fault, the fault branch cannot be correctly determined, which often results in a failure of ranging.
In order to solve the above problems, some innovative achievements appear in the prior art, such as: li Jie, Sun Ming river, Lijun, Gong Ling, Yang Guohua, a T-type line fault location system and method [ P ]. Sichuan: in patent documents CN106291256A,2017-01-04, a certain effect is obtained, but the distance measurement needs to be performed on each branch, so the algorithm positioning speed is not enough, and online monitoring cannot be realized.
The method has the advantages of reducing the influence of line parameter errors on distance measurement precision, improving the reliability of judging the fault branch of the T-shaped power transmission line, improving fault dead zones, improving the precision of fault distance measurement and the convergence speed, and having important significance on the stable and reliable operation of the T-shaped power transmission line. Therefore, a new fault location method is to be proposed for the T-type power transmission line.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a T-shaped line voltage cross correction fault location method based on dynamic real-time parameters, which mainly solves the following problems: 1) the problem that the distance measurement precision is affected due to the fact that the power transmission line parameters in practical engineering are easy to change is solved, and the power transmission line parameters are dynamically corrected in real time; 2) the problem that T node discrimination dead zones are prone to occur in a T-shaped line is solved, and whether a fault occurs in a certain branch or is close to the T node or not can be correctly discriminated; 3) the method and the device can ensure high-precision distance measurement of line faults and solve the problems of complex operation and multiple required iteration times of many existing distance measurement schemes.
The technical scheme adopted by the invention is as follows:
a T-shaped line voltage crossing correction fault location method based on dynamic real-time parameters utilizes electrical information of a T-shaped line in a normal operation state to dynamically calculate real-time parameters of three-end lines in real time, and corrects calculation errors of the real-time parameters of the lines based on a genetic algorithm; after the line has a fault, respectively calculating the voltage of the T node based on a line distribution parameter line model under the correction parameter, and judging a fault branch circuit through voltage comparison; then equating the two non-fault branches as a T end, and forming a two-end power transmission line model with one end of the fault branch; and finally, forming two straight lines by using the measured voltages at the two sides and the calculated voltage at the opposite side, and obtaining an intersection point based on the straight line intersection to form a fault distance measuring method.
The T-shaped line voltage cross correction fault location method based on the dynamic real-time parameters comprises the following steps:
dynamically calculating and correcting the real-time parameters of the T-shaped power transmission line:
step 1: measuring to obtain three-terminal voltage and current of the T-shaped power transmission line;
step 2: calculating the distributed voltage of the T node of the line along the three-terminal branch by using a distributed parameter model
Figure BDA0003146241770000021
Figure BDA0003146241770000022
And step 3: theoretically, the same T node voltage satisfies UT1＝UT2＝UT3(ii) a But because the parameters have errors, the fitness function is established by using the genetic algorithm
Figure BDA0003146241770000023
Wherein: j is the fitness function value, N is the number of sampling points of a cycle, UT1(i)、UT2(i)、UT3(i) Calculating the distribution voltage amplitude for the T node at the time i, setting the maximum evolution algebra N as 100 and the fitness function value J less than or equal to 1 percent as convergence conditions, and realizingAnd calculating parameter error correction.
The T-shaped line voltage cross correction fault location method based on dynamic real-time parameters is characterized by comprising the following steps:
and a T-shaped transmission line fault branch judgment step:
step 1: after the system fails, the distributed voltage of the T node at the moment is respectively calculated by utilizing dynamic calculation and correction of real-time parameters of the T-shaped power transmission line
Figure BDA0003146241770000024
Due to the fault branch of the line, the three obtained voltages are not equal.
Step 2: constructing fault branch criterion and direction criterion
Figure BDA0003146241770000025
Comparison criterion with amplitude
Figure BDA0003146241770000026
The direction comparison is used as a first criterion and the magnitude comparison is used as a second criterion.
Wherein: i, j corresponds to a non-fault branch, and k corresponds to a fault branch; k1,K2To determine the setting threshold value of the non-faulty branch, the parameter error is calibrated to be less than +/-5%, K1Take 0.95, K2Taking 1.05; k3For determining a threshold value for setting a faulty branch, according to the reliability principle, K3Take 1.15.
The T-shaped line voltage cross correction fault location method based on dynamic real-time parameters is characterized by comprising the following steps:
calculating equivalent two-end lines of the T-shaped three-end line: calculating equivalent voltage of a T node aiming at two ends of a non-fault branch by utilizing the fault branch judgment of the T-shaped power transmission line, the determined fault branch and the non-fault branch
Figure BDA0003146241770000031
And current
Figure BDA0003146241770000032
Wherein:
Figure BDA0003146241770000033
the current flowing into the point T is calculated from terminals N, P, respectively.
The T-shaped line voltage cross correction fault location method based on dynamic real-time parameters is characterized by comprising the following steps:
calculating fault location by linear intersection:
step 1: using equivalent two-terminal system voltage
Figure BDA0003146241770000034
And a current flowing between both ends
Figure BDA0003146241770000035
Respectively calculating the voltage amplitude U of the opposite side of the line based on a distributed parameter modelML、UTL. On the voltage planes distributed on both sides of the line, the voltage amplitude U is measured respectivelyM、UTAnd calculating the voltage amplitude UML、UTLEstablishing two straight lines and calculating the intersection point x1。
Step 2: using equivalent two-terminal system voltage
Figure BDA0003146241770000036
And a current flowing from both ends
Figure BDA0003146241770000037
Respectively calculating the intersection points x based on the distributed parameter model1Voltage amplitude UMx1、UTx1. On the voltage planes distributed on both sides of the line, the voltage amplitudes U are again measured separatelyM、UTAnd calculating the voltage amplitude UMx1、UTx1Establishing two new straight lines to find the intersection point x2。
And so on until the criterion | U is satisfiedMxn-UTxn|≤UsetAnd (6) ending. U shapeMxn、UTxnThe calculated voltage amplitudes for the nth time are respectively. U shapesetIs a threshold value Uset＝Min(|UM-UM03|,|UT-UT03|)，UM03、UT03Respectively calculating the distributed voltage values at 0.3km from the M end and the T end. At this time, the intersection x in the n-th calculation processnNamely the position of the fault point.
The T-shaped line voltage cross correction fault location method based on the dynamic real-time parameters is characterized by comprising the following steps of:
step 1: three-terminal voltage is measured respectively to three side trouble range unit of T type transmission line
Figure BDA0003146241770000038
Three terminal current
Figure BDA0003146241770000039
Step 2: respectively calculating the distributed voltage of the T nodes of the line along three ends by using a distributed parameter model,
Figure BDA00031462417700000310
Figure BDA0003146241770000041
Figure BDA0003146241770000042
wherein:
Figure BDA0003146241770000043
calculating voltages, gamma, for the T nodes along the MT, NT, PT branches, respectively1、γ2、γ3Respectively, the propagation constant, Z, of the three-terminal transmission lineC1、ZC2、ZC3Respectively, the characteristic impedance, L, of a three-terminal transmission line1，L2， L3The lengths of the three-terminal transmission lines are respectively;
and step 3: theoretically, the same T node voltage satisfies UT1＝UT2＝UT3(ii) a But because the parameters have errors, the fitness function is established by using the genetic algorithm
Figure BDA0003146241770000044
J is the fitness function value, N is the number of sampling points of a cycle, UT1(i)、UT2(i)、UT3(i) The distributed voltage amplitude is calculated for node T at time i. And setting the maximum evolution algebra N as 100 and the fitness function value J less than or equal to 1% as convergence conditions, and further realizing calculation parameter error correction.
And 4, step 4: after the system is in fault, respectively calculating the distributed voltage of the T node at the moment by using the correction parameters in the step 3
Figure BDA0003146241770000045
Figure BDA0003146241770000046
The three voltages must not be equal due to the presence of a faulty branch of the line.
And 5: and constructing a fault branch criterion. Direction criterion
Figure BDA0003146241770000047
Comparison criterion with amplitude
Figure BDA0003146241770000048
The direction comparison is used as a first criterion and the magnitude comparison is used as a second criterion. i. j corresponds to a non-fault branch, k corresponds to a fault branch; k1、K2To determine the setting threshold value of the non-faulty branch, the parameter error is calibrated to be less than +/-5%, K1Recommended 0.95, K2Recommended 1.05; k3For determining the setting threshold value of a faulty branch, K31.15 is recommended;
in step 5, the voltages of the non-fault branches are in the same direction and have the same amplitude; the voltage of the fault branch and the voltage of the non-fault branch are opposite, and the amplitudes are unequal. By analogy, the situation when the fault occurs in the NT and PT branches can be determined respectively. However, when a high-resistance ground fault occurs, the voltages of the faulty branch and the non-faulty branch may be in the same direction, but the amplitudes are still unequal. Thus, in conjunction with the above analysis, a directional comparison is constructed as a first criterion and a magnitude comparison is constructed as a second criterion. When a fault occurs near the T node, the three terminal calculated T node voltages will tend to be the same. For such a case, if it is assumed that an intra-area fault is known to occur, and neither direction comparison nor amplitude comparison can be determined, the fault is directly determined to be near the area, and can also be directly used as a fault distance measurement result.
Step 6: and after the T-type line fault branch is judged, the three-end line model is equivalent to a two-end line model. After the fault branch and the non-fault branch are determined, the equivalent voltage of the T node is calculated for the two ends of the non-fault branch
Figure BDA0003146241770000051
And current of
Figure BDA0003146241770000052
Wherein,
Figure BDA0003146241770000053
the current flowing into the point T is calculated from terminals N, P, respectively.
And 7: using equivalent two-terminal system voltage
Figure BDA0003146241770000054
And a current flowing from both ends
Figure BDA0003146241770000055
Respectively calculating the voltage amplitude U of the opposite side of the line based on a distributed parameter modelML、UTL. On the voltage planes distributed on both sides of the line, the voltage amplitude U is measured respectivelyM、UTAnd calculating the voltage amplitude UML、UTLEstablishing two straight lines and calculating the intersection point x1。
And 8: using equivalent two-terminal system voltage
Figure BDA0003146241770000056
And a current flowing between both ends
Figure BDA0003146241770000057
Respectively calculating the intersection points x based on the distributed parameter model1Voltage amplitude UMx1、UTx1. On the voltage planes distributed on both sides of the line, the voltage amplitudes U are again measured separatelyM、UTAnd calculating the voltage amplitude UMx1、UTx1Establishing two new straight lines and solving the intersection point x2. And so on until the criterion | U is satisfiedMxn-UTxn|≤UsetAnd (6) ending. U shapeMxn、UTxnThe calculated voltage amplitudes for the nth time are respectively. U shapesetIs a threshold value Uset＝Min(|UM-UM03|,|UT-UT03|)，UM03、UT03Respectively calculating the distributed voltage values at 0.3km from the M end and the T end. At this time, the intersection x in the n-th calculation processnNamely the position of the fault point.
The invention discloses a T-shaped line voltage cross correction fault location method based on dynamic real-time parameters, which has the beneficial effects that:
(1): line parameter errors can be dynamically adjusted in real time, fault location precision is improved, and engineering practicability is high;
(2): the problem of T node dead zone has been solved effectively, and the range finding principle is simple, only needs to carry out simple iteration, can reach the required precision of range finding.
(3): the ranging result has high precision and adaptability. The iteration frequency is less, the convergence speed is high, the distance measurement precision is high, and the calculated amount is small.
(4): the distance measurement result is not influenced by factors such as a system operation mode, transition resistance, fault types and the like.
Drawings
Fig. 1 is a T-line model under normal operation.
Fig. 2 is a converted double-ended fault line model.
Fig. 3 is a graph of amplitude distribution along a line voltage.
Fig. 4 is a schematic diagram of fault location.
Fig. 5 is a schematic diagram of fault ranging error correction.
Fig. 6(a) is a first simulation diagram of the ranging algorithm, where AG fault is Rg-100 Ω.
Fig. 6(b) is a simulation diagram of a ranging algorithm, where ABC fails, and Rg is 30 Ω.
Detailed Description
A T-shaped line voltage crossing correction fault location method based on dynamic real-time parameters utilizes electrical information of the T-shaped line in a normal operation state to dynamically calculate the real-time parameters of three-end lines in real time, and corrects calculation errors of the parameters based on a genetic algorithm; after the line has a fault, respectively calculating the voltage of the T node based on a line distribution parameter line model under the correction parameter, and judging a fault branch circuit through voltage comparison; further equating two non-fault branches as a T end, and forming a two-end power transmission line model with one end of the fault branch; and finally, forming two straight lines by using the measured voltages at the two sides and the calculated voltage at the opposite side, and obtaining an intersection point based on the straight line intersection to form fault distance measurement.
The distance measurement method comprises the following steps: dynamically calculating and correcting real-time parameters of the T-shaped power transmission line, judging fault branch of the T-shaped power transmission line, comprehensively judging line faults and measuring straight line crossing faults.
A novel T-shaped line voltage cross correction fault location method based on dynamic real-time parameters specifically comprises the following steps:
step 1: three-terminal voltage is measured respectively to three side trouble range unit of T type transmission line
Figure BDA0003146241770000061
Three terminal current
Figure BDA0003146241770000062
Step 2: respectively calculating the distributed voltage of the T nodes of the line along three ends by using a distributed parameter model,
Figure BDA0003146241770000063
Figure BDA0003146241770000064
Figure BDA0003146241770000065
FIG. 1 shows a T-line, L, in normal operation1，L2，L3The lengths of the three-terminal transmission lines are respectively,
Figure BDA0003146241770000066
is the voltage of the T-node,
Figure BDA0003146241770000067
calculating voltages, gamma, for the T nodes along the MT, NT, PT branches, respectively1、γ2、γ3Respectively, the propagation constant, Z, of the three-terminal transmission lineC1、ZC2、ZC3Respectively, the characteristic impedance of the three-terminal transmission line.
And step 3: and determining the identification parameters. Considering that the r, l and c values of the lines are generally used in the actual line parameter test, the model parameter { r to be identified by three ends is set based on the T-shaped line1、l1、c1、L1、r2、l2、c2、L2、r3、l3、c3、 L3-defining the line length parameter variation as L in order to distinguish between the inductance parameter and the line length. After the parameter error range is set, the basis can be found more easily by correcting the parameter error range, for example, the setting error range of the line parameters r, L and L is within +/-5%, and the error of the line parameter c is within +/-10%. Therefore, r is set at the time of actual parameter error calibrationo、lo、coAnd (3) substituting the line propagation constant and the line characteristic impedance formula to realize the final calculation of the distribution voltage of the formula (1).
Figure BDA0003146241770000071
Theoretically, the same T node voltage satisfies UT1＝UT2＝UT3(ii) a But because the parameters have errors, the fitness function is established by using the genetic algorithm
Figure BDA0003146241770000072
J is the fitness function value, N is the number of sampling points of a cycle, UT1(i)、UT2(i)、UT3(i) Distributed voltage amplitudes are calculated for the T nodes at i moments respectively. In the process of realizing parameter identification by using a genetic algorithm, the total number of groups is very huge according to the variable total dimension of 12 and the respective error ranges of +/-5% or +/-10%, even if the groups are established according to 1% of errors. Considering that the line parameters are optimized within the measurement error range and combined with the running time limit, the maximum evolution algebra m and the population size ps should be suitable and not too large. But the cross probability pc and the mutation probability pm are set relatively larger. It is emphasized here that the variation is to be distinguished from the 0-1 coding variation, but is to be random within the error range. According to the above analysis, the number of generations m of the substitution is 60, the population size ps is 1000, the cross probability pc is 0.5, and the variation probability pm is 0.15.
Besides the maximum evolution algebra as the convergence condition of the algorithm, the minimum value of the fitness function J is the key of function convergence. According to the condition that the voltages are equal, the two-phase value is zero, the fitness value is optimally zero, the error range is considered, and J is less than or equal to 1% and serves as a convergence condition, so that the error correction of the calculation parameters is realized.
And 4, step 4: after the system is in fault, respectively calculating the distributed voltage of the T node at the moment by using the correction parameters in the step 3
Figure BDA0003146241770000073
The three voltages must not be equal due to the presence of a faulty branch of the line.
And 5: and constructing a fault branch criterion. Direction criterion
Figure BDA0003146241770000074
Comparison criterion with amplitude
Figure BDA0003146241770000075
The direction comparison is used as a first criterion and the magnitude comparison is used as a second criterion. i. j corresponds to a non-fault branch, k corresponds to a fault branch; k1、K2To determine the setting threshold value of the non-faulty branch, the parameter error is calibrated to be less than +/-5%, K1Taking 0.95, K2Taking 1.05; k3For determining a threshold value for setting a faulty branch, according to the reliability principle, K3Take 1.15.
And 6: after the T-shaped line fault branch is judged, the fault location problem of the T-shaped line can be converted into the fault location problem of the transmission lines at two ends through equivalent calculation of non-fault branches.
Supposing that the fault branch is MT, and combining the calibration value of the transmission line parameters to obtain gammao、ZCoThe current flowing into the MT branch is calculated as
Figure BDA0003146241770000081
Wherein,
Figure BDA0003146241770000082
the current flowing into the point T is calculated from the terminals N, P, respectively, as shown in equation (2).
Figure BDA0003146241770000083
The voltage at the point T exists theoretically
Figure BDA0003146241770000084
But due to the existence of errors, choose
Figure BDA0003146241770000085
As the voltage at point T. At this time, the three-terminal line model is equivalent to a two-terminal line model, as shown in fig. 2, the line length is L, the fault point F is located on the MT line, and the distance is x from M terminal.
And 7: establishing two straight lines and solving an intersection point x1。
As shown in fig. 3, in the plane coordinate system, when the two ends are connectedAnd when the electric line has an internal fault, the voltage distribution along the line is obtained by calculation along two ends of the line respectively. The abscissa L corresponds to the length of the transmission line, and the ordinate is the magnitude of the voltage amplitude. Dotted line LMa、 LTaRespectively M, T along the voltage amplitude distribution curve. As can be seen from FIG. 3, the intersection point f of the two curvesaThe abscissa is the fault distance x. In the rectangular coordinate system, it is known that two non-parallel straight lines have to intersect and have only one point, and the intersection point coordinate can be conveniently and quickly positioned based on the straight line function. The method specifically comprises the following three parts:
1): obtaining the current and voltage measurement value of the equivalent two-end system
Figure BDA0003146241770000086
Calculating the voltage at the opposite end L based on the distributed parameter model
Figure BDA0003146241770000087
Figure BDA0003146241770000088
2): four-point coordinates are determined. From the formula (3), U can be obtainedML、UTLThe amplitude value is measured and combined with the voltage amplitude value U measured at the end of the line M, TM、UTThe calculated voltage point and coordinates (0, U) at two ends of the line can be obtainedTL)；(L，UML) Measuring voltage point, coordinate (0, U) at both ends of the lineM)；(L，UT). Respectively connected with coordinates (0, U)M) And (L, U)ML)， (L，UT) And (0, U)TL) So as to obtain two straight lines LMx1、LTx1。
3): after the straight line is determined, its intersection can be calculated:
Figure BDA0003146241770000091
in the formula (4), the solution (x) is obtained1，fx1) I.e. the coordinates of the intersection point. As shown in fig. 4, crossThe coordinate x is the actual fault point position and the abscissa x1Is the initial position of the measured fault point on the transmission line.
And 8: and correcting the primary ranging result. Using equivalent two-terminal system voltage
Figure BDA0003146241770000092
And a current flowing from both ends
Figure BDA0003146241770000093
Figure BDA0003146241770000094
Respectively calculating the intersection points x based on the distributed parameter model1Voltage amplitude U ofMx1、UTx1. On the voltage planes distributed on both sides of the line, the voltage amplitudes U are again measured separatelyM、UTAnd calculating the voltage amplitude UMx1、UTx1And obtaining a new coordinate point. Will (x)1，UMx1)、(x1，UTx1) Two straight lines are formed as new calculation points, and a new straight line intersection point (x) is obtained by using equation (5)2，fx2)。
Figure BDA0003146241770000095
By parity of reasoning, a new fault position x is obtained every timenThen, a general formula (6) is established, and a new fault location is established.
Figure BDA0003146241770000096
Until the criterion | U is satisfiedMxn-UTxn|≤UsetAnd (6) ending. U shapeMxn、UTxnThe calculated voltage amplitudes for the nth time are respectively. U shapesetIs a threshold value Uset＝Min(|UM-UM03|,|UT-UT03| to consider different situations such as the type of failure, the transition resistance, and the location of the failure, it is difficult to base the fixed value on the basis of the valuesThe threshold is determined. The threshold value is designed to at least meet the requirement of 300m voltage difference value by combining the requirement of line ranging error, such as 300m of a 220kV line. U shapeM03、UT03Respectively calculating the distributed voltage values at 0.3km from the M end and the T end. At this time, the intersection x in the n-th calculation processnNamely the position of the fault point. The schematic diagram of the error correction of the fault location and the simulation diagram are shown in fig. 5, 6(a) and 6 (b).
In FIG. 5, LMx2、LTx2The two straight lines obtained after the first correction are the intersection point (x)2，fx2) That is, the corrected fault location position is obviously obtained from fig. 5, and the corrected position is obviously close to the actual fault location position compared with the initial location.
The fault location simulation of straight line correction figures 6(a) and 6(b) well show the distribution trend of the location along the line,
the broken line L1 represents the distribution curve of the estimated voltage at the M terminal along the line;
the broken line L2 represents the distribution curve of the T-end estimated voltage along the line;
the solid line L3 represents a straight line one obtained by the M-side two-coordinate system;
the solid line L4 represents a line two obtained by the M-side coordinates.
Fig. 6(a) and 6(b) are both cases when an MT branch failure occurs. The broken line L1 and the broken line L2 respectively show the variation trend of the voltage amplitude distribution curve along the line from the end M and the end T, the intersection point of the two curves is a real fault point, the solid line L3 and the solid line L4 respectively show two straight lines obtained for the first time by using a straight line cross ranging method, and the intersection point of the two straight lines is a primary fault ranging point. It can be seen that the high ranging precision exists in the line through the initial ranging, wherein the highest ranging error of the whole line does not exceed 0.2km, and the high-precision ranging of the whole line can be realized.

Claims (1)

  1. The T-type line voltage cross correction fault location method is characterized by comprising the following steps:
    step 1: three-terminal voltage is measured respectively to three side trouble range unit of T type transmission line
    Figure FDA0003604294910000011
    Three terminal current
    Figure FDA0003604294910000012
    Step 2: respectively calculating the distributed voltage of the T nodes of the line along three ends by using a distributed parameter model,
    Figure FDA0003604294910000013
    Figure FDA0003604294910000014
    Figure FDA0003604294910000015
    wherein:
    Figure FDA0003604294910000016
    calculating voltages, gamma, for the T nodes along the MT, NT, PT branches, respectively1、γ2、γ3Respectively, the propagation constant, Z, of the three-terminal transmission lineC1、ZC2、ZC3Respectively, the characteristic impedance, L, of a three-terminal transmission line1，L2，L3The lengths of the three-terminal transmission lines are respectively;
    and step 3: theoretically, the same T node voltage satisfies UT1＝UT2＝UT3(ii) a But because the parameters have errors, the fitness function is established by using the genetic algorithm
    Figure FDA0003604294910000017
    J is the fitness function value, N is the number of sampling points of a cycle, UT1(i)、UT2(i)、UT3(i) Calculating the amplitude of the distributed voltage for the T node at the time i; setting the maximum evolution algebra N as 100 and the fitness function value J less than or equal to 1 percent asConverging conditions, and further realizing calculation parameter error correction;
    and 4, step 4: after the system is in fault, respectively calculating the distributed voltage of the T node at the moment by using the correction parameters in the step 3
    Figure FDA0003604294910000018
    Figure FDA0003604294910000019
    The three voltages must not be equal due to the presence of a faulty branch in the line;
    and 5: constructing a fault branch criterion; direction criterion
    Figure FDA00036042949100000110
    Comparison criterion with amplitude
    Figure FDA00036042949100000111
    The direction comparison is used as a first criterion, and the amplitude comparison is used as a second criterion; i. j corresponds to a non-fault branch, k corresponds to a fault branch; k is1、K2To determine the setting threshold value of the non-faulty branch, the parameter error is calibrated to be less than +/-5%, K1Take 0.95, K2Taking 1.05; k3For determining a threshold value for setting a faulty branch, according to the reliability principle, K3Taking 1.15;
    in step 5, the voltages of the non-fault branches are in the same direction and have the same amplitude; the voltage of the fault branch and the voltage of the non-fault branch are opposite, and the amplitudes are unequal; by analogy, the conditions of the faults occurring in the NT and PT branches can be respectively determined; when a high-resistance grounding fault occurs, the voltages of the fault branch and the non-fault branch can be in the same direction, but the amplitudes are still unequal; therefore, by combining the analysis, the direction comparison is constructed as a first criterion, and the amplitude comparison is constructed as a second criterion; when the fault occurs near the T node, the voltages of the three calculated T nodes tend to be the same; for the situation, if the fault in the known occurrence area is known and the direction comparison and the amplitude comparison cannot be distinguished, the fault is directly determined to be near the area and directly used as the fault distance measurement result;
    step 6: after a T-type line fault branch is judged, the three-end line model is equivalent to a two-end line model; after the fault branch and the non-fault branch are determined, the equivalent voltage of the T node is calculated for the two ends of the non-fault branch
    Figure FDA0003604294910000021
    And current
    Figure FDA0003604294910000022
    Wherein,
    Figure FDA0003604294910000023
    calculating the current flowing into the T point from N, P ends respectively;
    and 7: using equivalent two-terminal system voltage
    Figure FDA0003604294910000024
    And a current flowing between both ends
    Figure FDA0003604294910000025
    Respectively calculating the voltage amplitude U at the opposite side of the line based on a distributed parameter modelML、UTL(ii) a On the voltage planes distributed on both sides of the line, the voltage amplitude U is measured respectivelyM、UTAnd calculating the voltage amplitude UML、UTLEstablishing two straight lines and calculating the intersection point x1；
    And 8: using equivalent two-terminal system voltage
    Figure FDA0003604294910000026
    And a current flowing between both ends
    Figure FDA0003604294910000027
    Respectively calculating the intersection points x based on the distributed parameter model1Voltage amplitude UMx1、UTx1(ii) a On the voltage planes distributed on both sides of the line, the voltage amplitudes U are again measured separatelyM、UTAnd calculating the voltage amplitude UMx1、UTx1Establishing two new straight lines and solving the intersection point x2(ii) a And so on until the criterion | U is satisfiedMxn-UTxn|≤UsetFinishing; u shapeMxn、UTxnRespectively calculating voltage amplitude for the nth time; u shapesetIs a threshold value Uset＝Min(|UM-UM03|,|UT-UT03|)，UM03、UT03Respectively calculating the distributed voltage values at the positions of 0.3km respectively by the M end and the T end; at this time, the intersection x in the n-th calculation processnNamely the position of the fault point.
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